N,N′-(Biphenyl-2,2′-di­yl)bis­(furan-2-carboxamide)

Kee, C.H.; Thomas, N.F.; Ariffin, A.; Awang, K.; Ng, S.W.

doi:10.1107/S1600536809021874

organic compounds

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ISSN: 2056-9890

Volume 65| Part 7| July 2009| Page o1556

doi:10.1107/S1600536809021874

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N,N′-(Biphenyl-2,2′-diyl)bis(furan-2-carboxamide)

Chin Hui Kee,^a Noel F. Thomas,^a Azhar Ariffin,^a Khalijah Awang ^a and Seik Weng Ng ^a ^*

^aDepartment of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia
^*Correspondence e-mail: seikweng@um.edu.my

(Received 6 June 2009; accepted 9 June 2009; online 13 June 2009)

The title molecule, C₂₂H₁₆N₂O₄, is a 2,2′-disubstituted biphenyl whose phenylene rings are rotated by 66.5 (1)° so as to avoid repulsion by the substituents. Only one of the two amide –NH– fragments engages in hydrogen bonding, and this interacts with the amido –C(=O)– acceptor of an inversion-related molecule to generate a hydrogen-bonded dimer.

Related literature

The Heck reaction produces the desired stilbene along with a symmetrical biaryl owing to homocoupling of the aryl halide reactant. For the synthesis of stilbene carboxamides synthesized by using radical cations in a modified Heck reaction; see: Thomas et al. (2008 ).

Experimental

Crystal data

C₂₂H₁₆N₂O₄
M_r = 372.37
Triclinic, $[P \overline 1]$
a = 8.1784 (2) Å
b = 10.1399 (2) Å
c = 11.1475 (2) Å
α = 99.938 (1)°
β = 107.521 (1)°
γ = 92.439 (1)°
V = 863.92 (3) Å³
Z = 2
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 100 K
0.30 × 0.25 × 0.20 mm

Data collection

Bruker SMART APEX diffractometer
Absorption correction: none
6080 measured reflections
3836 independent reflections
3349 reflections with I > 2σ(I)
R_int = 0.015

Refinement

R[F² > 2σ(F²)] = 0.037
wR(F²) = 0.111
S = 1.03
3836 reflections
261 parameters
2 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.33 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2⋯O2ⁱ	0.88 (1)	2.12 (1)	2.970 (1)	165 (1)
Symmetry code: (i) -x+1, -y+1, -z+1.

Data collection: APEX2 (Bruker, 2008 ); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001 ); software used to prepare material for publication: publCIF (Westrip, 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809021874/tk2474sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809021874/tk2474Isup2.hkl

checkCIF report

Related literature top

Experimental top

N-(2-Iodophenyl)furan-2-carboxamide (1.51 g, 4.81 mmol) was dissolved in DMF (30 ml) under a nitrogen atmosphere. The solution was heated to 393 K. Palladium acetate (0.01 g, 0.05 mmol) was added followed by triethylamine (2.4 ml, 0.2 mol) and 4-methoxystyrene (0.83 g, 6.16 mmol). The mixture was heated for 48 h. The solution was cooled and then mixed with saturated sodium chloride. The organic compound was extracted with ethylacetate. The ethylacetate solution was dried with sodium sulfate. The solvent was evaporated and the product purified by column chromatography (0.12 g, 10% yield). Single crystals were obtained by recrystallization from hexane/chloroform.

Computing details top

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2009).

Figures top

	Fig. 1. Thermal ellipsoid plot (Barbour, 2001) of C₂₂H₁₆N₂O₄ at the 70% probability level. Hydrogen atoms are drawn as spheres of arbitrary radiius.
	Fig. 2. Hydrogen-bonded dimer in the crystal structure of (I). Red dashed lines represent N-H···O hydrogen bonds.

N,N'-(Biphenyl-2,2'-diyl)bis(furan-2-carboxamide) top

Crystal data top

C₂₂H₁₆N₂O₄	Z = 2
M_r = 372.37	F(000) = 388
Triclinic, P1	D_x = 1.431 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 8.1784 (2) Å	Cell parameters from 3508 reflections
b = 10.1399 (2) Å	θ = 2.6–28.3°
c = 11.1475 (2) Å	µ = 0.10 mm⁻¹
α = 99.938 (1)°	T = 100 K
β = 107.521 (1)°	Block, colorless
γ = 92.439 (1)°	0.30 × 0.25 × 0.20 mm
V = 863.92 (3) Å³

Data collection top

Bruker SMART APEX diffractometer	3349 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.015
Graphite monochromator	θ_max = 27.5°, θ_min = 2.0°
ω scans	h = −10→10
6080 measured reflections	k = −12→13
3836 independent reflections	l = −14→14

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.037	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.111	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ²(F_o²) + (0.0627P)² + 0.3539P] where P = (F_o² + 2F_c²)/3
3836 reflections	(Δ/σ)_max = 0.001
261 parameters	Δρ_max = 0.33 e Å⁻³
2 restraints	Δρ_min = −0.27 e Å⁻³

Crystal data top

C₂₂H₁₆N₂O₄	γ = 92.439 (1)°
M_r = 372.37	V = 863.92 (3) Å³
Triclinic, P1	Z = 2
a = 8.1784 (2) Å	Mo Kα radiation
b = 10.1399 (2) Å	µ = 0.10 mm⁻¹
c = 11.1475 (2) Å	T = 100 K
α = 99.938 (1)°	0.30 × 0.25 × 0.20 mm
β = 107.521 (1)°

Data collection top

Bruker SMART APEX diffractometer	3349 reflections with I > 2σ(I)
6080 measured reflections	R_int = 0.015
3836 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.037	2 restraints
wR(F²) = 0.111	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	Δρ_max = 0.33 e Å⁻³
3836 reflections	Δρ_min = −0.27 e Å⁻³
261 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
O1	0.37952 (12)	0.28756 (9)	0.22024 (9)	0.0174 (2)
O2	0.32912 (12)	0.61791 (9)	0.36569 (9)	0.0186 (2)
O3	0.42615 (12)	0.02447 (10)	0.82668 (9)	0.0213 (2)
O4	0.80281 (12)	0.23741 (9)	0.86550 (9)	0.0191 (2)
N1	0.29107 (14)	0.41257 (11)	0.42005 (10)	0.0156 (2)
H1	0.295 (2)	0.3271 (10)	0.3921 (17)	0.028 (5)*
N2	0.47787 (14)	0.16551 (11)	0.70037 (10)	0.0148 (2)
H2	0.5491 (17)	0.2298 (13)	0.6951 (15)	0.016 (4)*
C1	0.40891 (17)	0.24580 (13)	0.10565 (13)	0.0190 (3)
H1a	0.4304	0.1570	0.0749	0.023*
C2	0.40293 (17)	0.34894 (14)	0.04255 (13)	0.0190 (3)
H2a	0.4180	0.3456	−0.0391	0.023*
C3	0.36958 (16)	0.46370 (13)	0.12235 (12)	0.0173 (3)
H3	0.3581	0.5517	0.1044	0.021*
C4	0.35755 (16)	0.42216 (12)	0.22885 (12)	0.0155 (3)
C5	0.32496 (16)	0.49452 (12)	0.34438 (12)	0.0145 (2)
C6	0.24862 (16)	0.44495 (13)	0.53444 (12)	0.0144 (2)
C7	0.23946 (17)	0.57726 (13)	0.59222 (12)	0.0169 (3)
H7	0.2603	0.6501	0.5537	0.020*
C8	0.19978 (17)	0.60133 (13)	0.70591 (12)	0.0182 (3)
H8	0.1950	0.6913	0.7455	0.022*
C9	0.16695 (17)	0.49624 (14)	0.76291 (12)	0.0192 (3)
H9	0.1386	0.5138	0.8404	0.023*
C10	0.17609 (17)	0.36502 (13)	0.70536 (12)	0.0174 (3)
H10	0.1539	0.2928	0.7443	0.021*
C11	0.21726 (16)	0.33732 (12)	0.59167 (12)	0.0142 (2)
C12	0.21741 (16)	0.19410 (12)	0.53056 (12)	0.0142 (3)
C13	0.08880 (17)	0.13778 (13)	0.41514 (12)	0.0164 (3)
H13	0.0094	0.1937	0.3731	0.020*
C14	0.07515 (17)	0.00244 (13)	0.36117 (12)	0.0182 (3)
H14	−0.0121	−0.0337	0.2825	0.022*
C15	0.18976 (17)	−0.08003 (13)	0.42285 (12)	0.0178 (3)
H15	0.1790	−0.1734	0.3877	0.021*
C16	0.31983 (16)	−0.02613 (13)	0.53571 (12)	0.0161 (3)
H16	0.3991	−0.0826	0.5770	0.019*
C17	0.33501 (16)	0.11065 (12)	0.58905 (12)	0.0141 (2)
C18	0.52125 (16)	0.10827 (12)	0.80562 (12)	0.0150 (3)
C19	0.69553 (16)	0.15138 (12)	0.89706 (12)	0.0155 (3)
C20	0.77797 (18)	0.11564 (13)	1.01001 (13)	0.0195 (3)
H20	0.7319	0.0577	1.0529	0.023*
C21	0.94791 (18)	0.18268 (15)	1.05134 (13)	0.0226 (3)
H21	1.0380	0.1779	1.1272	0.027*
C22	0.95558 (18)	0.25413 (15)	0.96175 (13)	0.0226 (3)
H22	1.0546	0.3090	0.9652	0.027*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0214 (5)	0.0138 (4)	0.0181 (4)	0.0017 (4)	0.0076 (4)	0.0032 (3)
O2	0.0226 (5)	0.0136 (4)	0.0217 (5)	0.0018 (4)	0.0085 (4)	0.0058 (4)
O3	0.0197 (5)	0.0241 (5)	0.0206 (5)	−0.0031 (4)	0.0051 (4)	0.0095 (4)
O4	0.0162 (5)	0.0212 (5)	0.0196 (5)	−0.0015 (4)	0.0041 (4)	0.0065 (4)
N1	0.0211 (6)	0.0113 (5)	0.0162 (5)	0.0023 (4)	0.0082 (4)	0.0031 (4)
N2	0.0136 (5)	0.0140 (5)	0.0169 (5)	−0.0005 (4)	0.0037 (4)	0.0057 (4)
C1	0.0176 (6)	0.0193 (6)	0.0187 (6)	−0.0010 (5)	0.0066 (5)	−0.0011 (5)
C2	0.0166 (6)	0.0231 (6)	0.0170 (6)	−0.0003 (5)	0.0058 (5)	0.0029 (5)
C3	0.0160 (6)	0.0178 (6)	0.0185 (6)	0.0005 (5)	0.0056 (5)	0.0050 (5)
C4	0.0143 (6)	0.0132 (6)	0.0185 (6)	0.0005 (5)	0.0036 (5)	0.0044 (5)
C5	0.0124 (5)	0.0151 (6)	0.0158 (6)	0.0013 (4)	0.0031 (5)	0.0050 (5)
C6	0.0132 (6)	0.0158 (6)	0.0140 (6)	0.0022 (4)	0.0031 (5)	0.0039 (5)
C7	0.0176 (6)	0.0147 (6)	0.0177 (6)	0.0030 (5)	0.0038 (5)	0.0044 (5)
C8	0.0182 (6)	0.0163 (6)	0.0176 (6)	0.0056 (5)	0.0026 (5)	0.0012 (5)
C9	0.0198 (6)	0.0230 (7)	0.0143 (6)	0.0049 (5)	0.0048 (5)	0.0031 (5)
C10	0.0178 (6)	0.0192 (6)	0.0157 (6)	0.0015 (5)	0.0044 (5)	0.0060 (5)
C11	0.0120 (6)	0.0143 (6)	0.0148 (6)	0.0019 (4)	0.0016 (5)	0.0037 (4)
C12	0.0153 (6)	0.0140 (6)	0.0150 (6)	−0.0001 (5)	0.0063 (5)	0.0047 (5)
C13	0.0178 (6)	0.0162 (6)	0.0154 (6)	0.0026 (5)	0.0044 (5)	0.0053 (5)
C14	0.0194 (6)	0.0181 (6)	0.0153 (6)	−0.0015 (5)	0.0040 (5)	0.0018 (5)
C15	0.0211 (6)	0.0139 (6)	0.0193 (6)	−0.0002 (5)	0.0089 (5)	0.0018 (5)
C16	0.0157 (6)	0.0146 (6)	0.0202 (6)	0.0034 (5)	0.0078 (5)	0.0053 (5)
C17	0.0141 (6)	0.0156 (6)	0.0137 (6)	0.0000 (5)	0.0057 (5)	0.0040 (4)
C18	0.0154 (6)	0.0147 (6)	0.0156 (6)	0.0032 (5)	0.0055 (5)	0.0032 (5)
C19	0.0163 (6)	0.0147 (6)	0.0166 (6)	0.0018 (5)	0.0064 (5)	0.0036 (5)
C20	0.0205 (7)	0.0206 (6)	0.0171 (6)	0.0020 (5)	0.0049 (5)	0.0049 (5)
C21	0.0183 (7)	0.0283 (7)	0.0178 (6)	0.0018 (5)	0.0017 (5)	0.0023 (5)
C22	0.0152 (6)	0.0277 (7)	0.0219 (7)	−0.0026 (5)	0.0032 (5)	0.0024 (5)

Geometric parameters (Å, º) top

O1—C1	1.3695 (16)	C8—H8	0.9500
O1—C4	1.3749 (15)	C9—C10	1.3893 (18)
O2—C5	1.2295 (15)	C9—H9	0.9500
O3—C18	1.2267 (16)	C10—C11	1.3931 (18)
O4—C22	1.3613 (16)	C10—H10	0.9500
O4—C19	1.3716 (15)	C11—C12	1.4941 (17)
N1—C5	1.3572 (16)	C12—C17	1.3957 (18)
N1—C6	1.4093 (16)	C12—C13	1.4030 (17)
N1—H1	0.875 (9)	C13—C14	1.3853 (17)
N2—C18	1.3569 (16)	C13—H13	0.9500
N2—C17	1.4311 (16)	C14—C15	1.3884 (19)
N2—H2	0.877 (9)	C14—H14	0.9500
C1—C2	1.3521 (19)	C15—C16	1.3858 (18)
C1—H1a	0.9500	C15—H15	0.9500
C2—C3	1.4267 (19)	C16—C17	1.3961 (17)
C2—H2a	0.9500	C16—H16	0.9500
C3—C4	1.3550 (18)	C18—C19	1.4765 (18)
C3—H3	0.9500	C19—C20	1.3559 (18)
C4—C5	1.4715 (18)	C20—C21	1.4255 (19)
C6—C7	1.3999 (17)	C20—H20	0.9500
C6—C11	1.4067 (17)	C21—C22	1.345 (2)
C7—C8	1.3851 (18)	C21—H21	0.9500
C7—H7	0.9500	C22—H22	0.9500
C8—C9	1.3869 (19)

C1—O1—C4	106.32 (10)	C11—C10—H10	119.4
C22—O4—C19	105.90 (10)	C10—C11—C6	118.87 (12)
C5—N1—C6	129.64 (11)	C10—C11—C12	119.07 (11)
C5—N1—H1	114.1 (12)	C6—C11—C12	121.97 (11)
C6—N1—H1	116.3 (12)	C17—C12—C13	118.24 (11)
C18—N2—C17	122.19 (10)	C17—C12—C11	122.04 (11)
C18—N2—H2	118.8 (10)	C13—C12—C11	119.58 (11)
C17—N2—H2	118.2 (10)	C14—C13—C12	121.42 (12)
C2—C1—O1	110.34 (11)	C14—C13—H13	119.3
C2—C1—H1a	124.8	C12—C13—H13	119.3
O1—C1—H1a	124.8	C13—C14—C15	119.56 (12)
C1—C2—C3	106.73 (12)	C13—C14—H14	120.2
C1—C2—H2a	126.6	C15—C14—H14	120.2
C3—C2—H2a	126.6	C16—C15—C14	120.02 (12)
C4—C3—C2	106.31 (12)	C16—C15—H15	120.0
C4—C3—H3	126.8	C14—C15—H15	120.0
C2—C3—H3	126.8	C15—C16—C17	120.36 (12)
C3—C4—O1	110.30 (11)	C15—C16—H16	119.8
C3—C4—C5	131.50 (12)	C17—C16—H16	119.8
O1—C4—C5	118.19 (11)	C12—C17—C16	120.35 (11)
O2—C5—N1	125.53 (12)	C12—C17—N2	120.43 (11)
O2—C5—C4	120.77 (11)	C16—C17—N2	119.14 (11)
N1—C5—C4	113.70 (11)	O3—C18—N2	124.03 (12)
C7—C6—C11	120.02 (11)	O3—C18—C19	119.98 (12)
C7—C6—N1	122.95 (11)	N2—C18—C19	115.98 (11)
C11—C6—N1	117.03 (11)	C20—C19—O4	110.52 (11)
C8—C7—C6	119.61 (12)	C20—C19—C18	131.14 (12)
C8—C7—H7	120.2	O4—C19—C18	118.26 (11)
C6—C7—H7	120.2	C19—C20—C21	106.02 (12)
C9—C8—C7	121.07 (12)	C19—C20—H20	127.0
C9—C8—H8	119.5	C21—C20—H20	127.0
C7—C8—H8	119.5	C22—C21—C20	106.47 (12)
C8—C9—C10	119.20 (12)	C22—C21—H21	126.8
C8—C9—H9	120.4	C20—C21—H21	126.8
C10—C9—H9	120.4	C21—C22—O4	111.09 (12)
C9—C10—C11	121.23 (12)	C21—C22—H22	124.5
C9—C10—H10	119.4	O4—C22—H22	124.5

C4—O1—C1—C2	−1.04 (14)	C10—C11—C12—C13	109.90 (14)
O1—C1—C2—C3	0.66 (15)	C6—C11—C12—C13	−66.72 (16)
C1—C2—C3—C4	0.00 (14)	C17—C12—C13—C14	1.43 (19)
C2—C3—C4—O1	−0.65 (14)	C11—C12—C13—C14	−174.25 (11)
C2—C3—C4—C5	179.98 (13)	C12—C13—C14—C15	0.66 (19)
C1—O1—C4—C3	1.04 (14)	C13—C14—C15—C16	−1.8 (2)
C1—O1—C4—C5	−179.49 (11)	C14—C15—C16—C17	0.93 (19)
C6—N1—C5—O2	2.2 (2)	C13—C12—C17—C16	−2.34 (18)
C6—N1—C5—C4	−177.63 (12)	C11—C12—C17—C16	173.22 (11)
C3—C4—C5—O2	−11.2 (2)	C13—C12—C17—N2	174.26 (11)
O1—C4—C5—O2	169.42 (11)	C11—C12—C17—N2	−10.18 (18)
C3—C4—C5—N1	168.56 (13)	C15—C16—C17—C12	1.20 (18)
O1—C4—C5—N1	−10.77 (16)	C15—C16—C17—N2	−175.44 (11)
C5—N1—C6—C7	−1.9 (2)	C18—N2—C17—C12	133.43 (13)
C5—N1—C6—C11	178.99 (12)	C18—N2—C17—C16	−49.93 (17)
C11—C6—C7—C8	0.14 (19)	C17—N2—C18—O3	−15.7 (2)
N1—C6—C7—C8	−178.89 (12)	C17—N2—C18—C19	163.63 (11)
C6—C7—C8—C9	−0.7 (2)	C22—O4—C19—C20	0.32 (15)
C7—C8—C9—C10	0.7 (2)	C22—O4—C19—C18	−176.70 (11)
C8—C9—C10—C11	−0.1 (2)	O3—C18—C19—C20	−1.2 (2)
C9—C10—C11—C6	−0.48 (19)	N2—C18—C19—C20	179.49 (13)
C9—C10—C11—C12	−177.20 (12)	O3—C18—C19—O4	175.11 (11)
C7—C6—C11—C10	0.46 (18)	N2—C18—C19—O4	−4.22 (17)
N1—C6—C11—C10	179.55 (11)	O4—C19—C20—C21	−0.45 (15)
C7—C6—C11—C12	177.08 (11)	C18—C19—C20—C21	176.06 (13)
N1—C6—C11—C12	−3.83 (18)	C19—C20—C21—C22	0.40 (16)
C10—C11—C12—C17	−65.60 (16)	C20—C21—C22—O4	−0.22 (16)
C6—C11—C12—C17	117.78 (14)	C19—O4—C22—C21	−0.05 (15)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···O2ⁱ	0.88 (1)	2.12 (1)	2.970 (1)	165 (1)

Symmetry code: (i) −x+1, −y+1, −z+1.

Experimental details

Crystal data
Chemical formula	C₂₂H₁₆N₂O₄
M_r	372.37
Crystal system, space group	Triclinic, P1
Temperature (K)	100
a, b, c (Å)	8.1784 (2), 10.1399 (2), 11.1475 (2)
α, β, γ (°)	99.938 (1), 107.521 (1), 92.439 (1)
V (Å³)	863.92 (3)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.10
Crystal size (mm)	0.30 × 0.25 × 0.20

Data collection
Diffractometer	Bruker SMART APEX diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	6080, 3836, 3349
R_int	0.015
(sin θ/λ)_max (Å⁻¹)	0.650

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.037, 0.111, 1.03
No. of reflections	3836
No. of parameters	261
No. of restraints	2
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.33, −0.27

Computer programs: APEX2 (Bruker, 2008), SAINT (Bruker, 2008), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), X-SEED (Barbour, 2001), publCIF (Westrip, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···O2ⁱ	0.88 (1)	2.12 (1)	2.970 (1)	165 (1)

Symmetry code: (i) −x+1, −y+1, −z+1.

Acknowledgements

We thank the Malaysia Toray Science Foundation for supporting this study. CHK thanks MOSTI for an NSF scholarship.

References

Barbour, L. J. (2001). J. Supramol. Chem. 1, 189–191. CrossRef CAS Google Scholar
Bruker (2008). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Thomas, N. F., Kee, C.-H., Ariffin, A., Awang, K., Weber, J.-F. F., Lim, C.-G., Mukhtar, M. R. & Abdul Hadi, A. H. (2008). Heterocycles, 75, 1097–1108. CAS Google Scholar
Westrip, S. P. (2009). publCIF. In preparation. Google Scholar